Metabolic Capacity? Has Anyone Improved Theirs

Probably a question thatâ??s moreso directed to the guys & girls whoâ??ve competed or at least dieted to very low bodyfat levels for whatever reason one or more times in their life.

Thereâ??s some pretty prominent bodybuilding / physique coaches out there who claim itâ??s possible to increase the number of calories you can get / stay lean on over time (ie improve your metabolic capacity) and some even throw up examples of clients ect…

Has anyone here achieved anything similar ? Or are your numbers (macros / cals ect) always about the same when it comes time to really dial it in and get lean ?